This invention relates in general to a rotational driving and steering shaft assembly. More specifically, this invention relates to a steering shaft assembly using a ball spline as a slip member.
In virtually every vehicle in use today, a steering system is provided for permitting a driver to control the direction of movement. A typical steering system includes a steering wheel, a steering shaft assembly, and a steering device. The steering wheel is rotatably supported within a driver compartment of the vehicle for movement by a driver. The steering shaft assembly is connected at one end to the steering wheel for rotation therewith. The other end of the steering shaft assembly is connected to the steering device for turning the wheels of the vehicle in response to rotation of the steering wheel. In its simplest form, the steering shaft assembly is embodied as a single shaft or tube having a pair of yokes mounted on the ends thereof. The yokes are usually connected by respective universal joints to the steering wheel and the steering device.
In many larger vehicles, such as trucks, the steering shaft assembly is designed not only to provide a rotational driving connection between the steering wheel and the steering device, but also to permit relative axial movement to occur therebetween. Such relative axial movement is advantageous for two reasons. First, a relatively small amount of such relative axial movement is desirable to accommodate vibrations, bumps, and other aspects of normal vehicle operation that would otherwise be transmitted from the steering device through the steering shaft assembly to the steering wheel. Second, when the vehicle is serviced, a relatively large amount of such relative axial movement is desirable to permit the cab of the vehicle to be pivoted upwardly without requiring disassembly of the steering system.
To accomplish this, it is known to construct the steering shaft assembly from cooperating male and female splined telescoping steering shafts. The first steering shaft is connected to the steering wheel by a first universal joint, while the second steering shaft is connected to the steering device by a second universal joint. The universal joints are provided to permit angular articulation between the steering shafts and the associated steering wheel and the steering device. The splined connection between the first and second steering shafts provides a rotatable driving connection between the steering wheel and the steering device, while permitting relative axial movement therebetween.
In the past, one or both of the splined members were coated with a material having a relatively low coefficient of friction. The low friction coating was provided to minimize the amount of force required to effect relative movement between the two splined members. Also, the low friction coating provided a relatively tight fit between the cooperating splines of the two splined members, thus minimizing any undesirable looseness therebetween while continuing to allow free axial movement.
One problem that has been experienced in connection with slip members manufactured according to known methods is that an undesirably large gap can still exist between adjacent splines formed on the cooperating members of the slip member even after the coating has been applied. These relatively large gaps can occur as a result of manufacturing tolerances in the formation of the individual splined members and the coating process and usually result in an undesirable amount of looseness between the splined members during operation. Looseness that occurs in the direction of rotation of the splined members, wherein one of the splined members can rotate relative to the other splined member, is referred to as backlash. Looseness that occurs in the direction transverse to the axis of rotation of the slip member, wherein one of the splined member can extend at a cantilevered angle relative to the other splined member, is referred to as broken back. Known solutions to the problems of backlash and broken back have been found to be relatively difficult, costly, and time consuming to employ. Thus, it would be desirable to provide an improved slip member that results in precise conformance between the telescoping members, thus, minimizing the adverse effects of backlash and broken back.
This invention relates to a slip member for a steering shaft assembly. In one aspect of the invention, a slip member comprises an outer race member including one or more race tracks and an inner race member capable of being disposed within the outer race member. The inner race member includes a core member having one or more inner and outer race tracks corresponding in number to the one or more race tracks of the outer race member. The inner race member also includes a first end return member coupled to one end of the inner race member. The first end return member includes a recess defining a first end return track for allowing one or more ball bearings to recirculate between the outer race member and the inner race member. The inner race member also includes a second end return member coupled to the other end of the inner race member. The second end return member includes a recess defining a second end return track for allowing one or more ball bearings to recirculate between the outer race member and the inner race member. The one or more tracks of the outer race member radially aligns with the corresponding outer race track of the inner race member to define an outer ball recirculating track for transmitting torque between the outer race member and the inner race member through the one or more ball bearings. The one or more inner tracks of the inner race member defines an inner ball recirculating track for allowing the one or more ball bearings to freely travel between the inner ball recirculating track and the outer ball recirculating track.
In another aspect of the invention, a slip member comprises an outer race member including one or more race tracks, a yoke tube having at least one slot formed therein, a pair of ball recirculating track members disposed within the at least one slot, each ball recirculating track member including one or more recesses, the recesses forming an outer ball recirculating race track, an inner ball recirculating race track, and first and second end return race tracks; and one or more ball bearings disposed within one or the outer and inner ball recirculating race tracks.
In yet another aspect of the invention, a steering shaft assembly for a vehicle comprises a slip joint including an outer race member including one or more race tracks and an inner race member capable of being disposed within the outer race member. The inner race member includes a core member having one or more inner and outer race tracks corresponding in number to the one or more race tracks of the outer race member. The inner race member also includes a first end return member coupled to one end of the inner race member. The first end return member includes a recess defining a first end return track for allowing one or more ball bearings to recirculate between the outer race member and the inner race member. The inner race member also includes a second end return member coupled to the other end of the inner race member. The second end return member includes a recess defining a second end return track for allowing one or more ball bearings to recirculate between the outer race member and the inner race member. The one or more tracks of the outer race member radially aligns with the corresponding outer race track of the inner race member to define an outer ball recirculating track for transmitting torque between the outer race member and the inner race member through the one or more ball bearings. The one or more inner tracks of the inner race member defines an inner ball recirculating track for allowing the one or more ball bearings to freely travel between the inner ball recirculating track and the outer ball recirculating track. The second end return member including a shaft extending therefrom. A first yoke is secured to the shaft of the second end return member and the outer race member, and a second yoke secured to a yoke tube. The one or more tracks of the outer race member and the corresponding outer race track of the core member define an outer ball recirculating track for transmitting torque between the outer race member and the inner race member through the one or more ball bearings. The one or more inner tracks of the inner race member defines an inner ball recirculating track for allowing the one or more ball bearings to freely travel between the inner ball recirculating track and the outer ball recirculating track.
In yet another aspect of the invention, a steering shaft assembly for a vehicle comprises a slip joint including an outer race member including one or more race tracks, a yoke tube having at least one slot formed therein, a pair of ball recirculating track members disposed within the at least one slot, each ball recirculating track member including one or more recesses, the recesses forming an outer ball recirculating race track, an inner ball recirculating race track, and first and second end return race tracks, and one or more ball bearings disposed within one or the outer and inner ball recirculating race tracks. A first yoke is secured to the shaft of the outer race member and a second yoke secured to the yoke tube.
Various objects and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiments, when read in light of the accompanying drawings.